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Howlett" , Suren Baghdasaryan , linux-mm@kvack.org, willy@infradead.org, Laurent Dufour , Michel Lespinasse , Jerome Glisse , Vlastimil Babka , "Paul E. McKenney" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 866F514001A X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: rq3gy9xk8b9cf8n48qsepw8fy7gyw4ot X-HE-Tag: 1689174951-259758 X-HE-Meta: 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 NDfYv/0B HfUjkCc7SoaPM697Y73ajwbeSX/WcO6SSlQKfEz1BEEjOzAbPluxdp09R6ojOORxFeub7DBHcq9mQr8dSpwIECo0QPtb0cYF5kCSBw4+uJeS+pONUEw732eT2p+cgG82ncOoMWstxXht6aZUtOnDlC/PjyZAmL3Ng3wHrIL8GKjEz6boerQ8958TOBNiY+G8JMSUvzcSAGDnl+ut7qMKqiYA8mFIk+RzPBCm4BgU7nsqZpkMeXe0ftXSsxPNMIwffQjdH+mihOtL/ZkGLCcTXRT2eys/4kgwBvCCdmxZ+Fgu7+Nh21LSSrB8af6SDAVYABDcQGX3mGSuLUqY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jul 11, 2023 at 7:26=E2=80=AFPM Liam R. Howlett wrote: > > Suren, > > When running kselftest mm, I believe I've come across a lockdep issue > with the per-vma locking pagefault: > > [ 226.105499] WARNING: CPU: 1 PID: 1907 at include/linux/mmap_lock.h:71 = handle_userfault+0x34d/0xff0 > [ 226.106517] Modules linked in: > [ 226.107060] CPU: 1 PID: 1907 Comm: uffd-unit-tests Not tainted 6.5.0-r= c1+ #636 > [ 226.108099] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1= .16.0-debian-1.16.0-5 04/01/2014 > [ 226.109626] RIP: 0010:handle_userfault+0x34d/0xff0 > [ 226.113056] Code: 00 48 85 c0 0f 85 d4 fe ff ff 4c 89 f7 e8 bb 58 ea f= f 0f 0b 31 f6 49 8d be a0 01 00 00 e8 0b 8b 53 01 85 c0 0f 85 00 fe ff ff <= 0f> 0b e9 f9 fd ff ff 49 8d be a0 01 00 00 be ff ff ff ff e8 eb 8a > [ 226.115798] RSP: 0000:ffff888113a8fbf0 EFLAGS: 00010246 > [ 226.116570] RAX: 0000000000000000 RBX: ffff888113a8fdc8 RCX: 000000000= 0000001 > [ 226.117630] RDX: 0000000000000000 RSI: ffffffff97a70220 RDI: ffffffff9= 7c316e0 > [ 226.118654] RBP: ffff88811de7c1e0 R08: 0000000000000000 R09: ffffed102= 2991400 > [ 226.119508] R10: ffff888114c8a003 R11: 0000000000000000 R12: 000000000= 0000200 > [ 226.120471] R13: ffff88811de7c1f0 R14: ffff888106ebec00 R15: 000000000= 0001000 > [ 226.121521] FS: 00007f226ec0f740(0000) GS:ffff88836f280000(0000) knlG= S:0000000000000000 > [ 226.122543] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 226.123242] CR2: 00007f226ac0f028 CR3: 00000001088a4001 CR4: 000000000= 0370ee0 > [ 226.124075] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 000000000= 0000000 > [ 226.125073] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 000000000= 0000400 > [ 226.126308] Call Trace: > [ 226.127473] > [ 226.128001] ? __warn+0x9c/0x1f0 > [ 226.129005] ? handle_userfault+0x34d/0xff0 > [ 226.129940] ? report_bug+0x1f2/0x220 > [ 226.130700] ? handle_bug+0x3c/0x70 > [ 226.131234] ? exc_invalid_op+0x13/0x40 > [ 226.131827] ? asm_exc_invalid_op+0x16/0x20 > [ 226.132516] ? handle_userfault+0x34d/0xff0 > [ 226.133193] ? __pfx_do_raw_spin_lock+0x10/0x10 > [ 226.133862] ? find_held_lock+0x83/0xa0 > [ 226.134602] ? do_anonymous_page+0x81f/0x870 > [ 226.135314] ? __pfx_handle_userfault+0x10/0x10 > [ 226.136226] ? __pte_offset_map_lock+0xd4/0x160 > [ 226.136958] ? do_raw_spin_unlock+0x92/0xf0 > [ 226.137547] ? preempt_count_sub+0xf/0xc0 > [ 226.138011] ? _raw_spin_unlock+0x24/0x40 > [ 226.138594] ? do_anonymous_page+0x81f/0x870 > [ 226.139239] __handle_mm_fault+0x40a/0x470 > [ 226.139749] ? __pfx___handle_mm_fault+0x10/0x10 > [ 226.140516] handle_mm_fault+0xe9/0x270 > [ 226.141015] do_user_addr_fault+0x1a9/0x810 > [ 226.141638] exc_page_fault+0x58/0xe0 > [ 226.142101] asm_exc_page_fault+0x22/0x30 > [ 226.142713] RIP: 0033:0x561107c4967e > [ 226.143391] Code: 48 89 85 18 ff ff ff e9 e2 00 00 00 48 8b 15 49 a0 0= 0 00 48 8b 05 2a a0 00 00 48 0f af 45 f8 48 83 c0 2f 48 01 d0 48 83 e0 f8 <= 48> 8b 00 48 89 45 c8 48 8b 05 54 a0 00 00 48 8b 55 f8 48 c1 e2 03 > [ 226.145946] RSP: 002b:00007ffee4f22120 EFLAGS: 00010206 > [ 226.146745] RAX: 00007f226ac0f028 RBX: 00007ffee4f22448 RCX: 00007f226= eca1bb4 > [ 226.147912] RDX: 00007f226ac0f000 RSI: 0000000000000001 RDI: 000000000= 0000000 > [ 226.149093] RBP: 00007ffee4f22220 R08: 0000000000000000 R09: 000000000= 0000000 > [ 226.150218] R10: 0000000000000008 R11: 0000000000000246 R12: 000000000= 0000000 > [ 226.151313] R13: 00007ffee4f22458 R14: 0000561107c52dd8 R15: 00007f226= ee34020 > [ 226.152464] > [ 226.152802] irq event stamp: 3177751 > [ 226.153348] hardirqs last enabled at (3177761): [] = __up_console_sem+0x59/0x80 > [ 226.154679] hardirqs last disabled at (3177772): [] = __up_console_sem+0x3e/0x80 > [ 226.155998] softirqs last enabled at (3177676): [] = irq_exit_rcu+0x94/0xf0 > [ 226.157364] softirqs last disabled at (3177667): [] = irq_exit_rcu+0x94/0xf0 > [ 226.158721] ---[ end trace 0000000000000000 ]--- > > > CONFIG_PER_VMA_LOCK calls handle_mm_fault() in mm/memory.c > handle_mm_fault() may have an outdated comment, depending on what "mm > semaphore" means: > > * By the time we get here, we already hold the mm semaphore > > __handle_mm_fault+0x40a/0x470: > do_pte_missing at mm/memory.c:3672 > (inlined by) handle_pte_fault at mm/memory.c:4955 > (inlined by) __handle_mm_fault at mm/memory.c:5095 > > handle_userfault+0x34d/0xff0: > mmap_assert_write_locked at include/linux/mmap_lock.h:71 > (inlined by) __is_vma_write_locked at include/linux/mm.h:673 > (inlined by) vma_assert_locked at include/linux/mm.h:714 > (inlined by) assert_fault_locked at include/linux/mm.h:747 > (inlined by) handle_userfault at fs/userfaultfd.c:440 > > It looks like vma_assert_locked() is causing a problem if the mmap write > lock is not held in write mode. > > It looks to be an easy fix of checking the mmap_lock is held in write > mode in every other call location BUT the vma_assert_locked() path? Thanks Liam! Yes, the fix is indeed very simple. I missed the fact that __is_vma_write_locked() generates an assertion, which should probably be changed. I believe the same assertion is found by syzbot here: https://lore.kernel.org/all/0000000000002db68f05ffb791bc@google.com/#= t I'll post a fix shortly. BTW, this is happening only in mm-unstable, right? Thanks, Suren. > > Thanks, > Liam